Motivation

Specific leaf area (SLA, the ratio of leaf area to leaf dry mass) is an important trait for plant physiological, structural, and modeling analyses. SLA is also a useful measurement to upscale plant production, vegetation community composition, and other processes in Earth System Models, providing current-day benchmarks and improving predictions of future vegetation structure and function in terrestrial ecosystems.

We investigate SLA differences between plots of varying elevation and salinity exposure along a tributary of the Chesapeake Bay. The goals of this project are to (i) quantify SLA of eight major tree species, at multiple canopy heights, in temperate deciduous forests at the Smithsonian Environmental Research Center (Maryland, USA); and (ii) test for effects of soil moisture and saltwater exposure on SLA by comparing samples taken at shoreline and upland positions, with the shoreline samples taken along a ~2 km tidal creek that provided a natural salinity gradient.

Map of SERC with plots labeled:

Sampling Design

I think this would be a good place for methods

Figure 1: Collecting samples using a pole pruner

Figure 1: Collecting samples using a pole pruner

Figure 2: Collecting samples using a hand pruner

Figure 2: Collecting samples using a hand pruner

Figure 3: All the samples after a morning of collecting

Figure 3: All the samples after a morning of collecting

(I will evenually figure out how to only show the four species we are sampling from :) )

Characteristics of Species Sampled
Species Species Common Number of Trees Sampled Average Diameter (cm)
Acer rubrum Red maple 26 21.30
Carya glabra. Pignut hickory 6 20.28
Cornus florida. Flowering dogwood 2 3.20
Fagus grandifolia American beech 30 13.93
Liquidambar styraciflua Sweet gum 28 19.74
Liriodendron tulipifera Tulip poplar 14 37.11
Nyssa sylvatica Black gum 23 12.50
Quercus alba White oak 19 17.31

SLA Calculation

SLA is calculated using the ratio between a leaf’s one-sided fresh leaf area and its total dry mass.

sla <- sla %>% 
  mutate(specific_leaf_area = round(Leaf_Area_cm2 / Leaf_Mass_g, 3)) 
##      Date               Tag            No_Tag_Plot       
##  Length:148         Length:148         Length:148        
##  Class :character   Class :character   Class :character  
##  Mode  :character   Mode  :character   Mode  :character  
##                                                          
##                                                          
##                                                          
##                                                          
##  No_Tag_Species_code   No_Tag_DBH      Position            n_Leaves    
##  Length:148          Min.   : 1.10   Length:148         Min.   :4.000  
##  Class :character    1st Qu.: 8.00   Class :character   1st Qu.:6.000  
##  Mode  :character    Median :13.00   Mode  :character   Median :6.000  
##                      Mean   :15.31                      Mean   :5.831  
##                      3rd Qu.:21.10                      3rd Qu.:6.000  
##                      Max.   :49.60                      Max.   :9.000  
##                      NA's   :111                                       
##  Leaf_Area_cm2     Leaf_Mass_g        Notes           specific_leaf_area
##  Min.   :  5.23   Min.   :0.1810   Length:148         Min.   : 25.51    
##  1st Qu.:156.70   1st Qu.:0.6435   Class :character   1st Qu.:180.99    
##  Median :243.89   Median :0.9390   Mode  :character   Median :241.74    
##  Mean   :271.84   Mean   :1.2074                      Mean   :241.19    
##  3rd Qu.:357.00   3rd Qu.:1.6455                      3rd Qu.:295.35    
##  Max.   :914.19   Max.   :4.0270                      Max.   :563.18    
## 
##      Plot           Species_code           Tag                 DBH       
##  Length:471         Length:471         Length:471         Min.   : 1.80  
##  Class :character   Class :character   Class :character   1st Qu.: 8.85  
##  Mode  :character   Mode  :character   Mode  :character   Median :18.20  
##                                                           Mean   :22.69  
##                                                           3rd Qu.:34.15  
##                                                           Max.   :79.00
## Warning: We have blank species codes!

Average Specific Leaf Area

## Warning: Removed 3 rows containing missing values (geom_text_repel).

Specific Leaf Area by Species

Hmmm…. not sure where the top left species code went :/

The Relationship Between Specific Leaf Area and Tree Diameter at Breast Height